Exposure Diagnostic help please

[Stagecoach]

Sometimes we try to diagnose what we consider is a problem, never get to the bottom of it and wonder if we are missing something obvious. Perhaps it's just me but I would like to run this one through someone else as it's bugging me.

A few days ago Catalina posted an image which was a landscape consisting of 50% sky and 50% land and the posted image appeared on screen to be 'reasonably' exposed. By reasonable clipping could be removed by reducing exposure by -0.25 with a recovery of 60%.

The thread and image can be seen here A Cow

I looked at the Exif which is as follows;

Shooting Mode - PROGRAMMED AUTO
Aperture - f11
Speed - 1/500s
Exposure Compensation - -(minus) 4.7EV
Metering mode - Matrix
ISO - 400

What struck me was exposure compensation of -4.7 in programmed mode for a scene that I would have expected the camera to handle reasonably well. Following this I undertook some tests in the same mode, similar scene combination and came to the conclusion that if I had made a compensation of -4.7EV it would have produced a totally unusable result.

So the mystery was 'WHY' and 'HOW' the image posted was reasonable for which I came to two conclusions;

a) The camera was pointed at a very bright part of the sky when the metering system was locked at which time it also had the -4.7EV compensation set for some reason. The new scene was then framed, shutter operated and the image was luckily correct.

b) The posted image had not been corrected significantly due to severe underexposure because if blown up to 400% there is virtually no noise.

This is bugging me, what have I missed?

Grahame

[Colin Southern]

This is bugging me, what have I missed?

The fact that there was no actual EC used

[Stagecoach]

The fact that there was no actual EC used

That would explain things so why is it that when I look at the Exof in Opanda and Nikon ViewNX they both show exposure bias/compensation -4.7EV?

Grahame

[Colin Southern]

That would explain things so why is it that when I look at the Exof in Opanda and Nikon ViewNX they both show exposure bias/compensation -4.7EV?

Grahame

Dunno.

I checked the RAW data and saw an entry that would correspond to that, but neither Bridge nor Photoshop are reporting it, so looking like a technical glitch somewhere.

If you work it back from the Sunny 16 rule you should have 1/400th @ F16; in reality you have a wider aperture (F11) so shutterspeed would need to by 1/800th, and you have 1/500 - so by sunny 16 you'd be slightly over-exposed ...

... which is what we have. So no EC applied, despite the contradicting metadata.

[Stagecoach]

Dunno.

I checked the RAW data and saw an entry that would correspond to that, but neither Bridge nor Photoshop are reporting it, so looking like a technical glitch somewhere.

If you work it back from the Sunny 16 rule you should have 1/400th @ F16; in reality you have a wider aperture (F11) so shutterspeed would need to by 1/800th, and you have 1/500 - so by sunny 16 you'd be slightly over-exposed ...

... which is what we have. So no EC applied, despite the contradicting metadata.

Interesting one because some 80% of the images posted so far by Catalina show exposure compensation has been set. Makes it very difficult to diagnose anything if the data can't be trusted.

Grahame

[Colin Southern]

Interesting one because some 80% of the images posted so far by Catalina show exposure compensation has been set. Makes it very difficult to diagnose anything if the data can't be trusted.

Grahame

Oops - I must apologise Grahame - I was looking in the wrong place; Bridge is in fact showing the EC you're seeing, and Photoshop isn't showing it in the normal property window that I can see (even with an image of mine with EC applied).

So it's starting to look like the camera is simply lying to us.

[pnodrog]

Just read bits of the D40 manual. If the camera is set to Auto, EC is not active. I note the exif data Says Programmed Auto and with a value N2 - Maybe it is referring to the completely AUTO mode where EC is ignored (but reported?) not the Programme Mode where EC is active..

[Stagecoach]

Oops - I must apologise Grahame - I was looking in the wrong place; Bridge is in fact showing the EC you're seeing, and Photoshop isn't showing it in the normal property window that I can see (even with an image of mine with EC applied).

So it's starting to look like the camera is simply lying to us.

Colin,

I have just been running through all the images again, I have them all downloaded in one folder, and I'm starting to wonder the same. What bugs me now is that if this is the case it has caused me a lot of confusion but more importantly some help I have been giving has been based upon it

Can be sorted.

Grahame

[Stagecoach]

Just read bits of the D40 manual. If the camera is set to Auto, EC is not active. I note the exif data Says Programmed Auto and with a value N2 - Maybe it is referring to the completely AUTO mode where EC is ignored (but reported?) not the Programme Mode where EC is active..

Paul, I'm picking it up on Nikon ViewNX clearly defned 'Programmed Auto' but in Opanda as 'Normal Program'.

There has been a bit of a language/understanding problem but I can now concentrate on ensuring we are clear on exact which modes in use. I do know that there are a couple of shots in the series that show 'Manual' plus the compensation figure. Back to basics.

Grahame

[AB26]

Grahame,

Can you see any Exif data in this image of yours? I cannot see it. It is the second shot you took with -4.7 Ev.

If you can see the Exif and it has not changed, it will explain your question.



If I am on the right track then: Catalina has edited her image but the Exif remains as shot.

[Colin Southern]

Grahame,

Can you see any Exif data in this image of yours? I cannot see it. It is the second shot you took with -4.7 Ev.

If you can see the Exif and it has not changed, it will explain your question.



If I am on the right track then: Catalina has edited her image but the Exif remains as shot.

Doesn't add up for a couple of reasons:

1. You can't apply EC in that camera mode, and

2. If you apply the exposure used, the result was exactly as expected with no EC (which backs up #1).

Plus with that much EC really applied and at that ISO you'd have buckets of noise.

[Stagecoach]

Grahame,

Can you see any Exif data in this image of yours? I cannot see it. It is the second shot you took with -4.7 Ev.

If you can see the Exif and it has not changed, it will explain your question.

If I am on the right track then: Catalina has edited her image but the Exif remains as shot.

Andre,

Thanks for coming in on this one, I can not see any Exif using either tools I have with this image of mine you have posted, whereas I can see it on my original.

The image is the one I took in 'Programmed Mode' (P) and applied -4.7EV

a) There is no question to me that you have edited this by increasing exposure for the sky in post because the noise is very noticeable when viewed larger. The Catalina image showed absolutely no appreciable noise even at 400%?

b) Exif data for shooting parameters will not change as far as I'm aware after having done PP.

I can also produce a similar result to what you have by pushing up exposure plus fill light and can also use noise removal, but, these are things we have learnt to do in PP and I do not suspect Catalina has the skills or tools to do this.

I'm sure you can understand my concern in that if an image had been PPd to correct a very poor exposure the EC would suggest an incorrect or not realised practice at the time of taking the shot

I'll get there, eventually

Grahame

[AB26]

I'm sure you can understand my concern in that if an image had been PPd to correct a very poor exposure the EC would suggest an incorrect or not realised practice at the time of taking the shot

I'll get there, eventually

Grahame

Grahame,

If you are using a Nikon: Go into your camera Menu, adjust exposure value to overexpose by 2 or 3 stops. Then set your camera to Program Auto and without compensating for exposure see what your camera produces. You should get a shot that is 3 stops overexposed although the exposure meter has indicated that exposure was correct. Now press the ± button and dial in -4.7 EC. Your shot should now be underexposed by 1.7. Correct it in PP and see what the Exif data shows you.

It is possible that Catalina’s camera is set up “incorrectly” in the Menu. Hence the massive EC she has to apply.

Well I am glad for this thread. Gives me something to do and makes me learn more about camera settings.

[deetheturk]

Should av bought a Canon!!!

[AB26]

Doesn't add up for a couple of reasons:

1. You can't apply EC in that camera mode, and

Wrong Colin, you can when shooting a Nikon. In "P" mode you simply press the +- button and dial in EC.

PS: Read the review of the D40. 6MP CCD sensor showing very little noise at ISO400.

Whenever the dynamic range in a scene is very narrow high ISO does not render lots of noise.

[AB26]

Should av bought a Canon!!!

With NO EC in "P" mode? Might as well get a P&S.

[Ken MT]

With my Canon 5D mk 2 I can change the EC in program mode, so what is the difference

[pnodrog]

With NO EC in "P" mode? Might as well get a P&S.

I think Colin was referring to Programme Auto mode where EC is not available and you are confusing it with "P" mode where it is available and yes Programme Auto mode is a point and shoot mode available on a D40.

[AB26]

I think Colin was referring to Programme Auto mode where EC is not available and you are confusing it with "P" mode where it is available and yes Programme Auto mode is a point and shoot mode.

I dunno what camera you are using. On mine "P" does not mean Professional, it actually means Programmed Auto. On my camera and on the D40 EC is available in "P" mode.

PS: My camera does not have the "A" for P&S. The D40 does have that mode.

[pnodrog]

I dunno what camera you are using. On mine "P" does not mean Professional, it actually means Programmed Auto. On my camera and on the D40 EC is available in "P" mode.

Have a look at the mode dial on top of a D40 "P" and "Auto" are both there are you telling me they are the same?